How do I prevent windows opening on one of my desktops?

How do I prevent windows opening on one of my desktops?

I have 2 monitors and a tv screen connected to my computer. The tv is angled so I can watch it in bed but is facing away from my desk (and usually switched off). Sometimes applications open on the monitor and I have to fiddle around with the "Move" menu option to bring them back to one of the screens I can see.